Just suggesting you give a bit more info:
Do you want to sell stock photos through a library?
or do you want an agent, to sell your photography?

The former is a relationship in which you supply captioned pics and they sell to publishers etc, and send you a quarterly cheque or whatever. The latter is a working relationship between a photographer and a go-between who actively seeks work and liaises with cuustomers.

Also, what style and subject matter is your body of work? A wildlife photographer will choose a different stock library to a social documentary photographer. If you are a generalist, you should seek a generalist library, but these are (normally) the least productive in income, simply because you are competing in a larger field.

To step down, there are on-line libraries that range from seriously good to very casual, with income potentials proportionate. And there are on-line portals on which you do everything, including dealing with picture buyers. Some charge an annual subscription fee.

There are stories of photographers selling one image for six figures, but generally it's pocket money and a numbers game. A commonly quoted rule of thumb is $1-2 per year per image lodged.

There are many decisions you need to make before choosing an agent. Asking around is a good idea, but perhaps have a think and an on-line explore, and then ask more specific questions.

I think I want to sell stock but all the places i looked at were either for the paparazzi specialists of just free stock. And the 6 figure pic was a very revealling photo of some celeb i think. Also this info is great, how do you know all about it? Did you try to go pro or are you pro? Thanks again.

That's a different six-figure pic, so there's more than one out there! The one I refer to was sold through Ozimages (an Australian based on-line library - the type photographers subscribe to and sell their own work via).

I never saw the image but I was chatting with the photographer one day and he said it sold to a corporation for use as their theme image. He was working in a camera shop on a Saturday morning when I met him so you have to wonder!

If I were you I would do another on-line search. Hit Google or something but type in photo library Scottish landscapes or cat breeds or whatever you like to shoot. That way you will find the stock outfits that handle your kind of subject matter.

I'm a grey-whiskered professional wildlife photographer. Though on a salary now, stock has been an important part of my patchy income for 30 years. I work with Auscape International, PhotoResearchers and Ecoscene. They are all theme libraries with some prestige.

Stock went downhill in the digital age for a number of reasons, but quality images still command reasonable prices. That's why I suggested you gather a really classy body of work and go to the top libraries. The rest are chaff selling chaff.

But it takes time and effort to get a lot of top images in your portfolio. That's what separates the wheat from the chaff.